Seriously though, all these extra dimensions people amke up each week are nothing but theoretical, mathematical constructs which have never had any basis in reality. How could anyone describe such things? In what terms? It has X height, Y length, and Z depth? It's blue? It tastes like lemon? I'll accept that these ideas about heaps of other dimensions are more than simply an excuse to employ mathematicians when someone can deliver some evidence that they are more than just theoretical constructs.

Many people get confused when talking about extra dimensions. Some get ideas in their heads that were spawned in Science fiction.
Others trash the idea of extra dimensions because we observe only three spacial dimensions and one time and like adam assume them to be made up "to employ mathematicians".
Well, firstly let me put asside any fanciful ideas of the extra dimensions being completely different to our 3 +1. They are spacial.
In string theory, point particles are actually really small loops of energy. (I'm no expert so anyone who is please explain this better than I can) if the string is on a 2D plane, it can only vibrate in 2 different ways, back/forth and left/right. Put in 3D space it can vibrate three ways. I've no idea why because it's a very complex framework but for string theory to work the string needs to vibrate 9 different ways! Strings are very very small (on average the plank length ~10^-35 ish m) so there is no problem in the extra 6 dimensions it needs being wrapped up very small into a "calabi-yau" shape. These extra dimensions are tacked onto every point in our extended three.
Don't try and visualise this 9 dimensional space, we can't because we've spent so long in our 3 that we just can't.
These curled up dimensions don't affect our three dimensions, but they do have an impact on the universe.
The vibrational patterns of strings give the properties of the particles they appear to us as. These vibrational patterns are affected by the curled up 6 dimns so they are shown through the properties in the particles we observe.

Adam,
A lot of statistical analyses are multidimensional. If you do a fit to data with 10 different variables, it is a 10-dimensional system. A lot of these analyses are useful including in microarray analyses looking at gene expression and have 10k+ dimensions. Not everything has to be about the physical world.

In string theory, point particles are actually really small loops of energy. (I'm no expert so anyone who is please explain this better than I can) if the string is on a 2D plane, it can only vibrate in 2 different ways, back/forth and left/right. Put in 3D space it can vibrate three ways. ...... so there is no problem in the extra 6 dimensions it needs being wrapped up very small into a "calabi-yau" shape. These extra dimensions are tacked onto every point in our extended three.

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no problem? Any direction they vibrate to is 3D. Problem solved. If you want more, then you are dreaming.

Don't try and visualise this 9 dimensional space, we can't because we've spent so long in our 3 that we just can't.

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god works in mysterious way? sorry, as long as supersting theory hasn't been experimented on (I don't expect this to happen tomorrow), I can only laugh at the idea of 10-11 dimensions like I laugh at a christian praying to "god". You can add as many variables in statistics as you want, that still doesn't make them for real!

C'est,
If the last comment is directed towards me then you're an idiot. All I was saying is that mathematically you can easily have a real 10 dimensional parameter space. Nothing to do with 10 physical dimensions, yet it is a 10 dimensional space by definition.

I must also say that considering something that hasn't been experimented on laughably false is a bit contrary to the concept of progress in science. Before a theory is demonstrated experimentally it describes reality just as well as after, the only difference is in our confidence in it.

It's true that these extra dimensions in string theory haven't been discovered, but there nature in the theory means that their existence does not contradict what we see.
I'm not saying that there ARE extra dimensions, nor am I trying to convince anyone that there are by using string theory which as you pointed out is untested (but very promising).
The original question in this thread was could anyone describe the extra dimensions. I answered by saying that they are spacial dimensions under string theory.
I strongly reccomend 'The elegant universe' It's a fantastic book which explains a lot about new ways of viewing the universe. It's primarily about string theory but there's also a very good chapter on relativity which has made the theory click for me.

that's one hell of an explanation of why nobody has ever been able to prove these little extra-dimension theories: "It's beyond us." Sounds an awful lot like religion...

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The reason no-one can see the direct effect of the dimensions, or the strings themsleves is because they're so small.

As to why we can't prove the extra dimensions, that's because to prove their existence you must confirm the theory. To do that you must make predictions. One prediction that string theory makes is supersymetry. This is for particle phycisists to discover because it means another particle to be discovered for each known particle. Superpartners . The masses of these are not known accurately but they are estimated to be within the capabilities of the new particle accelerator being built at CERN, scheduled for 2004.
This prediction however is not unique to string theory. Unique predictions are proving difficult to extract from the very complex mathematical framework of string theory, which is by no means complete.
The fact that the theory is as yet untested is simply because this is the first time that theorists are racing ahead of experimantal phycisists. The technology is not there to test the theory directly so new more devious ways of testing it must be found. These will come in time, but the theory is so promising in it's power to explain the universe on the most fundamental level that those who laugh should just let it be, because there's no reason for trashing the theory yet.

"The reason no-one can see the direct effect of the dimensions, or the strings themsleves is because they're so small. "

you're just repeating what you've been told
it's nonsense to say this
okay for the strings, I love the idea of strings, but saying that we cannot detect the effect of the dimensions because of size is equal to whitchcraft, it says nothing, it's not science
may I also remind you that the experimental confirmation requires such amounts of energy that you'll probably be death by the time they can do that, that the string theory is simply their last hope for the holy grail and that's the reason it has (finally) succes amongst physicians (but certainly not all!!)

"You can add as many variables in statistics as you want, that still doesn't make them for real!"

by definition there are real examples of multidimensional spaces greater than 4 even if the spatiotemporal world is limited to 4. You seemed to suggest that such things aren't real.

I never said that an unporven theory should be an argument for the existence of extra spatial dimensions. I just think a theory that fits current knowledge is worthy of consideration and not laughable.

I also never said that analogies should be accepted as proof. They are a useful way of carrying over understanding from one area to another. I have never even heard of anyone thinking they should be accepted as proof. In fact in logic they are considered incorrect and dangerous. I never used any analogies anyway so I'm not even sure what you're talking about.

You can call me friend if you want, but I don't want to be friends with anyone as dogmatic and close minded as yourself. I guess I shouldn't have called you an idiot though and I appologize for that, it was unnecessary and rude. I just feel your approach to interacting in any thread I've observed to take away and not add, and was hoping you might start thinking about what you have to say more thoroughly if I insulted you. As this clearly resulted in more comments of questionable utility I will drop this strategy in the future.

If I may I'd like to use a dreaded analogy. You may have seen it before but it's relavent nontheless.

A garden hose stretching accross a small ravine. You view it from half a mile away. All you can see is a line. If you imagined a bug on the hose, you could give its position with one number, its distance along the hose. From your distant viewpoint this hose is one dimensional. Now look at it through a pair of binoculars and you see that it's two dimensional. You give the bugs position by two numbers, it's distance along the hose and the distance around the circumference of the hose.

Just a brief insight into how small curled up dimensions can become undetectable. In string theory the 6 extra dimensions are in a calabi-yau shape, which is a proven mathematicaly possible 6 dimensional shape. There are thousands of these shapes and as yet there is no way of plucking one particular one from the theory. But, it's possible and doesn't in ANY way contradict what we observe.

Posted by ElmoSome get ideas in their heads that were spawned in Science fiction.

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And some scientifically fictitious ideas spawn real advancements in science, such as quantum entanglement, microwave telephony and satcomms (et al).

All

So what I'm hearing here is that the higher 'known' dimensions are not proven. That any reference to them or referant from them is purely mathematical?

Is this a fair interpretation of your posts?

Also, I haven't seen it proven but have heard and accepted the theory that as we know we have d1,2 and 3 (x,y,z) and then d4 (time).

The proposal is that d5 is some probability or selective alternate option function, meaning simply that if all possible universes are happening simultaneously then imagine that they are aligned on a line and positions on that line can be read as with other dimensions.

Empirically, the theory is that the probability that an entity inhabits constitutes it's 5th dimension.